Your students will love this way of using art to inspire ideas. I love the stream of consciousness idea using handwriting and images. When you allow your students to open their minds to free thought - no inhibition - and include art or nature, there is no stopping their creative responses!
This site gives step-by-step instructions for facilitating a brainstorming session in your classroom. I especially like the pie and card method; it engages students both individually and as a team of learners.
There are ten links here to music that can be using to stimulate students' thinking. Teachers can ask the students to draw or write while listening or they can use the music as jumping off points for a story, playwriting or debate.
I have used carousels as a brainstorming activity. The students enjoy it because they get to move around the classroom and look at their peers' comments. If students are put into groups and use a specific color for each groups, then you could have groups report out on the end based on their "color" contributions.
I love this activity and will try it this year! The timer brings excitement to the activity and also makes students more engaged on each moment with each other. Furthermore, it gives students the opportunity to work with multiple partners in learning.